The present invention relates to the field of semiconductor device manufacturing and more particularly to methods for forming layers on a semiconductor substrate using physical vapor deposition.
Ionized metal plasma physical vapor deposition (INP-PVD) is commonly used to deposit conductive metal and metal-containing films onto semiconductor substrates. It is particularly useful for forming layers within high aspect ratio openings. A cross-section illustrating portions of a typical IMP-PVD chamber design is shown in FIG. 1. The cross-section includes a chamber 10, a sputtering target 12, a shield 14, a coil 16, a pedestal 18, and a semiconductor substrate 19. During normal operation, the target 12 is biased such that ions from a plasma are accelerated towards the target, whereby they strike it and xe2x80x9csputterxe2x80x9d atoms off of the target and onto the substrate 19, thereby forming a layer on the substrate 19. The coil 16 provides a variety of functions during the IMP-PVD deposition process including generating ions that sputter the target 12, heating electrons in the plasma so they can more efficiently ionize gas molecules, and additionally, ionizing atoms sputtered from the target and providing an additional sputtering source for depositing material onto the substrate.
FIG. 2 includes a top-down view of the IMP-PVD chamber shown in FIG. 1 illustrating portions of the shield 14, the coil 16, and the semiconductor substrate 10. Additionally included in FIG. 2 are ceramic support pins 22, which electrically insulate the coil 16 and the shield 14, and ceramic feed through pins 24. In addition to electrically insulating the coil 16 and the shield 14, the ceramic feed through pins 24 serve as conduits for electrically coupling the coil 16 to an external power source. Additionally, the ceramic support pins 22 and feed through pins 24 physically support the coil 16 in the chamber and are the coil""s primary heat transfer agent (i.e. the primary source for dissipating heat generated by the coil) during the deposition process. Prior art IMP-PVD chambers that utilize coils and ceramic pins 22 and 24 may be adequate for low coil power applications (less than 2.5 kilowatts), however they may not be suitable for higher coil power applications (greater than 2.8 kilowatts).
Increasing the power applied to the coil has been found to have a number of processing advantages. Increasing the coil power increases the number of ionized species available at the substrate surface, which can improve the step coverage and uniformity of the layer being deposited. This can be particularly useful for depositing films such as copper films and copper barrier films into high aspect ratio openings. In addition, the increased coil power increases the overall deposition rate, which has the potential for increasing process throughput and providing additional process control. However, increasing the power applied to the coil using the prior art chamber configuration can also negatively impact processing because the increase in power can uncontrollably heat the coil. This can undesirably affect the deposition process and negatively impact the mechanical integrity of the coil. The uncontrolled changes in the coil temperature can influence the grain size and sputter rate of the coil""s material and correspondingly produce uncontrolled changes in the uniformity and step coverage of the deposited film. This necessitates using throughput-limiting cooling steps during deposition process to prevent coil overheating. Finally, the prior art ceramic pin chamber configuration may be insufficient for controlling or preventing electrical coupling between the coil 16 and the shield 14 which can become problematic at higher coil powers